Separate an experiment from a live service
A prototype can help you check whether customers understand an idea before paying for a complete build. For a live pilot, identify the limits of each free tier and what happens when you exceed them. Include database storage, file uploads, email delivery, backups and support time in your operating budget.
What to prepare for your project
Write down the one task your pilot must support and the number of users you expect. This makes it easier to choose a practical starting point and estimate what will need a paid service.